High frequency generator



1934- c. w. RICE HIGH FREQUENCY GENERATOR Filed Aug. 27, 1950 mlmmmllmmlwllmmmmmm Hg. 3. I FL 4.

Inventor Chester W. RLce HLS Attorney.

Patented Aug. 7, 1934 UNITED STATES I HIGH FREQUENCY GENERATOR ChesterW. Rice, Schenectady, N. Y., assig'nor to General Electric Company, acorporation of New York Application August 2'7, 1930, Serial No. 478,143

6 Claims.

My invention relates to high frequency generators, and more particularlyto generators for producing oscillations of ultra-short wave length as,for example, wave lengths in the order of a few centimeters.

Still more particularly my invention relates to oscillation generatorsof the general type disclosed by Dr. Albert W. Hull in an articlepublished February, 1918, in the Proceedings of the Institute of RadioEngineers,- volume 6. In this article is indicated an electron dischargeoscillation generator in which oscillations are set up in an oscillatorycircuit connected in series with an electron receiving electrode, whichmay be designated as the plate, of the discharge device, thisoscillatory circuit comprising shunt-connected inductance and capacity.The discharge device is one of the type in which the anode is interposedbetwen the cathode and the said plate, or third electrode, and in whichwhen the anode is supplied with suitable positive potential it impartsto the circuit of the plate, or third electrode, a negative resistancecharacteristic over a certain range of plate voltage variation.

That is, for example, as the voltage of the plate is increased-from zerothe current in the plate circuit will increase until a point is reachedat which emission of secondary electrons from the plate takes place, dueto bombardment of the plate by electrons emitted from the cathode, thesesecondary electrons being attracted to the more positive anode. Uponfurther increase in the plate potential the plate current starts todecrease and may continue to decrease to zero, depending upon thepotential of the anode, at which time the number of secondary electronsemitted from theplate equals the number of primary electrons which hitthe plate. Upon further increase in plate potential the plate currentreverses and increases to a maximum in the opposite direction. At thislatter maximum the potential of the anode is no longer sufiicient todraw all of the secondary electrons away from the plate. The platecurrent accordingly decreases to zero and then builds up in the oppositedirection.

In that range of plate voltage variation between the two maxima, thecircuit of-the plate has negative resistance; that is, the platecurrent-plate voltage characteristic has a negative slope and in thisrange, oscillations may be produced dependent uponthe amount ofinductance, capacity and resistance in the circuit.

My invention relates to certain improvements in generators of the typeindicated, and it has for one of its objects to construct a generatorofthis type capable of producing oscillations of ultra-high frequency.

My invention relates more particularly to the structure of the dischargedevice employed, and it has for a further object to provide a dischargedevice capable of operating in the manner above explained and whichincludes either within itself, or as a part of its structure, theelements of the necessary oscillatory. circuit.

The novel features which I believe to be characteristic of my inventionare set forth with particularity in the appended claims. My inventionitself, however, both as to its organization and method of operation,together with further objects and advantages thereof may' best beunderstood by reference to the following description taken in connectionwith the accompanying drawing in which Fig. 1 represents an embodimentof my invention, and Figs. 2, 3 and 4 represent modifications thereof.

Referring to Fig. 1 I have shown therein an electron discharge devicecomprising an evacuated envelope 1 having oppositely extendingprotuberances 2 and 3. Within the envelope 1 are a cathode structure 4,an electron receiving electrode 5, which I have above referred to as theplate, and an additional electron receiving electrode, or anode, 6interposed between the cathode and plate. The cathode structure 4 is ofwell known form, and is supported from the protuberance 2. The cathodeis arranged within a cylinder 4' whereby the emitted electrons arefocused in a stream directed toward the plate 5. It is arranged to beheated to incandescence by means of a source of potential 14. The plate5 is supported from the protuberance 3 and isarranged opposite thecathode structure 4. The anode comprises an annular conducting member 6having an aperture 7 therein, this aperture being arranged in alignmentwith the cathode and the 5 plate thereby to permit electrons emittedfrom the cathode readily to pass through the aperture 7 to the plate 5.This annular electrode 6 is supportedtfrom a third protuberance 8 of theenvelope 1. Lead-in conductors for the different electrodes extendthrough the ends of the respective protuberance of the envelope 1.

The electrode 6 is maintained at a high positive potential with respectto the cathode by means of a'source of potential 9, the negative side ofwhich is connected to the source 14 and to the cathode. The plate isconnected to an intermediate point upon the source 9, such that itspotential is positive with respect to the cathode but negative withrespect to the third 1 10 electrode.

In accordance with my invention I so arrange the elements of thedischarge devicethat the oscillatory circuit in which oscillations areproduced by the device may be entirely enclosed within the envelope 1.This oscillatory circuit comprises the plate 5 and a member 10 which maybe suitably mounted within the protuberance 3 and which may have atubular portion 11 extending from the protuberance and terminating in aplate member or disc 12 which extends laterally of the device andpreferably parallel to the surface of the plate 5.

The plate electrode 5 is constituted by the end of a rigid bar member 13extending from the disc 12 to which it is secured. If desired the plateelectrode 5 may comprise a plate like top member secured to the end ofthe bar 13 thereby to give the electrode an electron receiving area ofdesired dimensions. The surface thereof may be treated in any suitableway to produce a maximum of emission of secondary electrons. Thus theplate electrode structure may take the form of a stool projecting fromthe disc 12, the bar portion 13 forming the single leg of the stool andthe structure serving as the radiating member of the system.

The member 10 has a large surface area and thereby forms a capacitycounter-poise for the device in that its large capacity to groundprevents rapid variations in the potential of this member duringoperation of the system. The bar 13 has inductance suflicient toresonate at a very high frequency with the capacity existing between theplate members. 5 and 12 and the capacity element 10, this capacitycomprising principally that between the parallel plates 5 and 12. Thedimensions of the plate 5 and the bar 13 may be such that the frequencyat which this inductance and capacity resonates is very high as in theorder of a few centimeters of wave length.

With the potentials impressed upon the plate 5 and third electrode 6such that the device operates upon the negative resistance portion ofits characteristic curve, the device is in a state of unstableequilibrium described in the abovementioned article with the result thathigh frequency oscillations will be excited in the resonant circuitcomprising the plate members 5, l3 and the capacity element 10. The bar13 together with the plate 5 will then operate as an antenna orradiator, to radiate into space the high frequency oscillationsgenerated, these oscillations having a frequency determined by theinductance and capacity of the oscillatory circuit.

As pointed out in the above mentioned article, the conditions foroscillation in a circuit of the type indicated are such that thenegative resistance r must be less than in which L, C and R representthe inductance,

capacitance and the resistance of the oscillatory circuit respectively,the resistance, of course, in-

' eluding both the ohmic resistance and radiation resistance. By varyingthe proportions of the radiating circuit, that is, the length anddiameter of the bar, or stem 13, and the size of the end portion, or topthereof, the radiation resistance of the structure can be adjusted and,therefore, the value of of the envelope 1 the tubular portion 11 thereofbeing supported about the protuberance 3 of the envelope. The member 10is connected to the outer end of the radiating member 13 thereby tomaintain it at a substantially constant potential.

In Fig. 3 I have shown as above indicated a further modification of theinvention in which the radiating member 13 is given a certain amount ofadditional inductance by arranging it in the form of a helix or coil.

In Fig. 4 I have shown an arrangement in which the end of the radiatingmember 13, which serves as the plate electrode, is reduced in itsdimensions to the cross-sectional area of the radiating member. In thisway the capacity between the plate and the member 10 may be reduced.

To modulate the oscillations produced in a generator of the typeindicated a fourth electrode, not shown, may be interposed between theelectrode 6 and the cathode, and its potential varied in accordance withdesired signals. This method of modulation is described in theabove-mentioned article. Other means for modulating the oscillationsproduced may also be employed.

While I have shown particular embodiments of my invention it will ofcourse be understood that I do not wish to be limited thereby, sincemany other modifications in the form and arrangement of the elements maybe made, and I therefore contemplate by the appended claims to cover anysuch modifications as fall within the true spirit and scope of myinvention.

What I claim as new and desire to secure by Letters Patent. is: v

1. An electron discharge device having a cathode and a capacity element,said capacity element being spaced apart from said cathode and having amember projecting therefrom toward the cathode to form anelectron'receiving electrode, said member having inductance sufiicientto resonate at a desired frequency with the capacity existing betweenthe capacity element and said member.

2. The combination, in an electron discharge device, of a cathode, aconducting member disposed apart therefrom, a second conducting membermounted within said discharge device to form a radiator, said conductingmember being conductively connected at one end to said first member andmounted to receive electrons at the other end from said cathode, saidfirst member having sufficiently large'surface area to preventsubstantial high frequencyvariation in potential during operation ofsaid device and said second member having sufiicient inductance toresonate with. the capacity between the two members.

3. In combination, an electron discharge device comprising a cathode. anelectron receiving electrode spaced apart therefrom, and a secondelectron receiving electrode interposed between said cathode and saidfirst mentioned electron receiving electrode and mounted to attractelectrons from the first electron receiving electrode when electrons areemitted therefrom by reason of bombardment of electrons from thecathode, a capacity member having'large surface area, and a conductiveconnection between the first mentioned electron receiving electrode andsaid capacity member having inductance suilicient to resonate at highfrequency with the capacity between said capacity member, said firstelectron receiving electrode, and connection, the area of said capacitymember being sufficient to prevent substantial variation in potentialthereof at said high frequency.

4. In combination, an electron discharge device having a cathode, anelectron receiving electrode, a radiating member mounted to support saidelectron receiving electrode at one end thereof,

means for maintaining the opposite end of said radiating member atground alternating potential, a third element disposed in proximity tosaid electron receiving electrode, said third element and electronreceiving electrode being adapted to have potentials impressed thereonof such value that said device operates upon an unstable portion of thecharacteristic expressing the relation between current flowing in saidelectron receiving electrode and the voltage impressed thereon, and saidradiating member being mounted to oscillate at high frequency thereby tocause said electron receiving electrode potential to oscillate throughthe value corresponding to said unstable portion of the characteristic,whereby high frequency oscillations are main tained upon said radiatingmember.

5. In combination, an electron discharge device, comprising an envelopeand a plurality of pacity to resonate with'the inductance thereof at thefrequency of oscillations to be produced, a cathode, and means forfocusing primary electrons emitted from said cathode upon one end ofsaid member, an additional member mounted to receive electrons from saidfirst member when said first member'is bombarded with electrons fromsaid cathode whereby when electromotive force is supplied to saidelectrodes of desired value oscillations are generated on said rigidmember.

CHESTER W. RICE.

